1. Field of the Invention
The present invention relates to an HDTV signal transmission apparatus for transmitting HDTV video signals multiplexed to the STM-16 (synchronous transport module-16) frame, the transmission frame of the new digital synchronous network, "SDH (synchronous digital hierarchy) network", based on CCITT recommendations G707, G708, and G709 ("CCITT recommendations" below).
2. Description of the prior art
Transmission apparatuses for transmitting full-band HDTV digital signals ("HDTV signals" below) using the SDH network have been developed in recent years. It is essential to use a fiber-optic transmission path when transmitting uncompressed full-band HDTV signals because of the high bit rate. When used for transmission between broadcasting stations or for live broadcasts, however, transmission distances commonly exceed several ten kilometers, and long-distance laying of private fiber optic cables is extremely expensive and difficult. The SDH network is therefore used for HDTV signal transmission because of its high bit rate capacity.
A conventional HDTV signal transmission apparatus for transmitting a 10-bit/word, YPbPr-format HDTV signal (e.g., SMPTE 260M (Society of Picture and Television Engineers)) using an SDH network is described below. Note that this HDTV signal transmission apparatus comprises the HDTV signal transmitter, HDTV signal receiver, and the transmission path.
A conventional HDTV signal transmitter comprises a luminance signal input terminal to which the HDTV luminance signal is input; a color difference multiplexing signal input terminal to which the HDTV color difference multiplexing signal is input; a first time divider for 1:4 time-based dividing the HDTV luminance signal; a second time divider for 1:4 time-based dividing the HDTV color difference multiplexing signal; a C4 container device for multiplexing the 1:4 time-divided luminance and color difference multiplexing signals to sixteen C4 containers; an STM-16 framing device for multiplexing the sixteen C4 containers to the STM-16 frame according to CCITT recommendations; and an STM-16 frame output terminal for outputting the STM-16 frame.
The conventional HDTV signal transmitter thus comprised operates as follows. The HDTV luminance signal input from the luminance signal input terminal is separated into four separated luminance signals by the first time divider. The HDTV color difference multiplex signal input from the color difference multiplex signal input terminal is separated into four separated color difference multiplex signals by the second time divider. Each of the four series of separated luminance signals and separated color difference multiplex signals is multiplexed to two C4 containers, resulting in a total sixteen multiplexed C4 containers. The sixteen multiplexed C4 containers are then multiplexed to the STM-16 frame by the STM-16 framing device, and output from the STM-16 frame output terminal to the transmission path.
A conventional HDTV signal receiver comprises an STM-16 frame input terminal to which the STM-16 frame carried over the transmission path is input; an STM-16 framing device for demultiplexing the sixteen C4 containers from the STM-16 frame according to the CCITT recommendations; a C4 deframing device for demultiplexing the four time-divided separated luminance signals and separated color difference multiplex signals from the sixteen C4 containers; a first time-division multiplexer for time-division multiplexing the four separated luminance signals; a second time-division multiplexer for time-division multiplexing the four separated color difference multiplex signals; a luminance signal output terminal for outputting the HDTV luminance signal; and a color difference multiplex signal output terminal for outputting the HDTV color difference multiplex signal.
This conventional HDTV signal receiver operates as follows. The STM-16 frame is input from the STM-16 frame input terminal. The STM-16 framing device demultiplexes the sixteen C4 containers from the input STM-16 frame. The C4 deframing device demultiplexes the four time-base separated luminance signals and color difference multiplex signals from the sixteen C4 containers. The first time-division multiplexer multiplexes the four separated luminance signals to the HDTV luminance signal, and outputs the multiplexed luminance signal from the luminance signal output terminal. The second time-division multiplexer multiplexes the four separated color difference multiplex signals to the HDTV color difference multiplex signal, and outputs the result from the color difference multiplex signal output terminal.
The problem with this conventional configuration, however, is that relatively large-scale circuitry is required because a YPbPr-format HDTV signal is multiplexed to all sixteen C4 containers, and all of these C4 containers are multiplexed to the payload of the STM frame. In addition, because unused bandwidth is distributed to all C4 containers, it is difficult to transmit a GBR-format HDTV video signal, or to add additional functionality using this unused bandwidth to transfer audio signals, control signals, or other non-HDTV signals.